Nathalie Mitton

Mobility prediction based neighborhood discovery in mobile Ad Hoc networks

Hello protocol is the basic technique for neighborhood discovery in wireless ad hoc networks. It requires nodes to claim their existence/ aliveness by periodic hello messages. Central to a hello protocol is the determination of hello message transmission rate. No fixed optimal rate exists in the presence of node mobility. The rate should in fact adapt to it, high for high mobility and low for low mobility. In this paper, we propose a novel mobility prediction based hello protocol, named ARH (Autoregressive Hello protocol). Each node predicts its own position by an ever-updated autoregression-based mobility model, and neighboring nodes predict its position by the same model. The node transmits hello message (for location update) only when the predicted location is too different from the true location (causing topology distortion), triggering mobility model correction on both itself and each of its neighbors. ARH evolves along with network dynamics, and seamlessly tunes itself to the optimal configuration on the fly using local knowledge only. Through simulation, we demonstrate the effectiveness and efficiency of ARH, in comparison with the only competitive protocol TAP (Turnover based Adaptive hello Protocol) [9]. With a small model order, ARH achieves the same high neighborhood discovery performance as TAP, with dramatically reduced message overhead (about 50% lower hello rate).

A Turnover based Adaptive HELLO Protocol for Mobile Ad Hoc and Sensor Networks

We present a turnover based adaptive HELLO protocol (TAP), which enables nodes in mobile networks to dynamically adjust their HELLO messages frequency depending on the current speed of nodes. To the best of our knowledge, all existing solutions are based on specific assumptions (e.g., slotted networks) and/or require specific hardware (e.g., GPS) for speed evaluation. One of the key aspects of our solution is that no additional hardware is required since it does not need this speed information. TAP may be used in any kind of mobile networks that rely on HELLO messages to maintain neighborhood tables and is thus highly relevant in the context of ad hoc and sensor networks. In our solution, each node has to monitor its neighborhood table to count new neighbors whenever a HELLO is sent. This turnover is then used to adjust HELLO frequency. To evaluate our solution, we propose a theoretical analysis based on some given assumptions that provides the optimal turnover when these assumptions hold. Our experimental results demonstrate that when this optimal value is used as the targeted turnover in TAP, the HELLO frequency is correctly adjusted and provides a good accuracy with regards to the neighborhood tables.

Reliable Routing in Vehicular Ad Hoc Networks

One of the notoriously difficult problems in vehicular ad-hoc networks (VANET) is to ensure that established routing paths do not break before the end of data transmission. This is a difficult problem because the network topology is constantly changing and the wireless communication links are inherently unstable, due to high node mobility. In this paper we classify existing VANET routing protocols into five categories: connectivity-based, mobility-based, infrastructure-based, geographic-location-based, and probability-model-based, according to their employed routing metrics. For each category, we present the general design ideas and state of the art. Our objective is to attract more attention to the VANET routing problem and encourage more research efforts on developing reliable solutions.

End-to-End energy efficient geographic path discovery with guaranteed delivery in ad hoc and sensor networks

We propose a novel localized routing protocol for wireless sensor networks (WSN) that is energy-efficient and guarantees delivery. We prove that it is constant factor of the optimum for dense networks. To forward a packet, a node s in graph G computes the cost of the energy weighted shortest path (SP) between s and each of its neighbors which are closer to the destination than itself. It then selects node x which minimizes the ratio of the cost of the SP to the progress towards the destination. It then sends the message to the first node on the SP from s to x: say node x. Node x restarts the same greedy routing process until the destination is reached or the routing fails. To recover from failure, our algorithm invokes face routing that guarantees delivery. This work is the first to optimize energy consumption of face routing. First, we build a connected dominating set from graph G, second we compute its Gabriel graph to obtain the planar graph G. Face routing is applied on G only to decide which edges to follow in the recovery process. On each edge, greedy routing is used. This two-phase (greedy-Face) end-to-end routing process (EtE) reiterates until the final destination is reached. Simulation results show that EtE outperforms several existing geographical routing on energy consumption metric.

Cost over Progress Based Energy Efficient Routing over Virtual Coordinates in Wireless Sensor Networks

We propose an energy efficient routing protocol, VCost, for sensor networks. We assume that nodes are unaware of their geographic location thus, VCost assigns virtual coordinates to nodes as follows. Based on the node hop count distances from a set of landmarks, our method computes a distance metric to obtain the nodes virtual coordinates. VCost, then uses these coordinates to route packets from node u to node v, in its neighborhood, such that the ratio of the cost to send a message to v to the progress in the routing task towards the destination is minimized. Compared to existing algorithms that use virtual locations, our simulation shows that VCost improves significantly energy consumption and preserves the small percentage of successful routings.

Greedy Geographic Routing Algorithms in Real Environment

Existing theoretical and simulation studies on georouting appear detached from experimental studies in real environments. We set up our test environment by using WSN430 wireless sensor nodes. To overcome the need for significant number of wireless nodes required to perform a realistic experiment in high density network, we introduce a novel approach - emulation by using relatively small number of nodes in 1-hop experimental setup. Source node is a fixed sensor, all available sensors are candidate forwarding neighbors with virtual destination. Source node makes one forwarding step, destination position is adjusted, and the same source again searches for best forwarder. We compare three georouting algorithms. We introduce here Greedy geographical routing Algorithms in a REal environment (GARE)which builds a RNG by using ETX(uv)|uv| as edge weight (ETX(uv)counts all transmissions and possibly acknowledgments between two nodes until message is received), and selects RNG neighbor with greatest progress toward destination (if none of RNG neighbors has progress, all neighbors are considered). Our experiments show that GARE is significantly more efficient than existing XTC algorithm (applying RNG on ETX(uv)) in energy consumption. COP GARE selects neighbor with progress that minimizes ETX(uv)|uv|, and outperforms both algorithms.

Routing in wireless networks with position trees

Sensor networks are wireless adhoc networks where all the nodes cooperate for routing messages in the absence of a fixed infrastructure. Non-flooding, guaranteed delivery routing protocols are preferred because sensor networks have limited battery life. Location aware routing protocols are good candidates for sensor network applications, nevertheless they need either an external location service like GPS or Galileo (which are bulky, energy consuming devices) or internal location services providing non-unique virtual coordinates leading to low delivery rates. In this paper we introduce Position Trees a collision free, distributed labeling algorithm based on hop counting, which embed a spanning tree of the underlying network. The Routing with Position Trees (RTP) is a guaranteed delivery, non-flooding, efficient implicit routing protocol based on Position Trees. We study experimentally the statistical properties of memory requirements and the routing efficiency of the RPT.

Decentralized Pull-Based Information Gathering in Vehicular Networks Using GeoVanet

A vehicular ad hoc network (VANET) is a type of mobile network whose nodes are traveling cars and which communicate with one another using short-range wireless communications. These cars can exchange and share different information among them, which can lead to the development of interesting applications that require the cooperation of vehicles or using the vehicular network as a distributed computing platform. Along with the opportunities offered by vehicular networks, a number of challenges also arise. In this paper, we focus on information gathering in vehicular ad hoc networks by using a pull model. Such model would allow users to send queries to a set of cars in order to find the desired information. In order to propose such a query processing scheme, the main challenge to address is how to route the different results towards their recipient in a highly dynamic network where the nodes move very quickly. To solve this, we propose GeoVanet, a DHT-based geographic routing protocol which ensures that the sender of a query can get a consistent answer. Our goal is not to compute the query result instantaneously but to ensure that the user will be able to retrieve it within a bounded time. To prove the effectiveness of GeoVanet, an experimental evaluation is provided, which shows that up to 80% of the available query results are delivered to the user.

Hector is an Energy Efficient Tree-Based Optimized Routing Protocol for Wireless Networks

This paper considers the problem of designing power efficient routing with guaranteed delivery for sensor networks with known distances between neighbors but unknown geographic locations. We propose Hector, a hybrid energy efficient tree-based optimized routing protocol, based on two sets of virtual coordinates. One set is based on rooted tree coordinates, and the other is based on hop distances toward several landmarks. In our algorithm, the node currently holding the packet forwards it to its neighbor that optimizes ratio of power cost over distance progress with landmark coordinates, among nodes that reduce landmark coordinates and do not increase tree coordinates. If such a node does not exist then forwarding is made to the neighbor that reduces tree based distance and optimizes power cost over tree distance progress ratio. Our simulations show the superiority of our algorithm over existing alternatives while guaranteeing delivery, and only up to 30% additional power compared to centralized shortest weighted path algorithm.

Towards unified tag data translation for the Internet of Things

Following the “Internet of Things” concept, each object will be associated with a unique identifier which will allow to retrieve information about it in large databases. In the process of retrieving information, this identifier (ID) may have to be translated into different formats (e.g. domain name style format for object name service query, binary, legacy,…). The Tag Data Translation (TDT) is responsible for the translation of IDs into these different formats. We propose a general TDT system which extends the standards of EPCGlobal which only targets Electronic Product Code (EPC). We integrate other RFID and smart cards standards (such as ISO 14443 and 15693) and GS1 standards which are more general as they also deal with bar code (EAN/UPC).